Dual exhaust benefits

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How about coated or wrapped 2.25" shorty headers? Maybe lose 4 degrees from the exhaust lobe and add it to the intake? (250/250 @ .050") They were only playing with a 9.8:1 single carb .030" over 427. Maybe use a 1.8 intake rocker and run the cam straight up. Maybe 108/108, a little tighter for the small engine than at 110.

I wouldn't draw any conclusions about exhaust tuning from that Hot Rod article. (Or anything else they publish)
 
Originally Posted by userfriendly
How about coated or wrapped 2.25" shorty headers? Maybe lose 4 degrees from the exhaust lobe and add it to the intake? (250/250 @ .050") They were only playing with a 9.8:1 single carb .030" over 427. Maybe use a 1.8 intake rocker and run the cam straight up. Maybe 108/108, a little tighter for the small engine than at 110.

I wouldn't draw any conclusions about exhaust tuning from that Hot Rod article. (Or anything else they publish)


In that article they used one set up to compare different headers, it wasn't meant to find the absolute most that that engine would produce. Everything works as a system.

And what works on one engine combination, won't work as good on another. Smaller engine making less power won't need as big of pipes.
 
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Originally Posted by userfriendly
It makes sense to me that exhaust velocity would be higher in large diameter pipes because heat travels to cold.


Too big of a pipe and the exhaust velocity will drop at low rpm.
 
I always thought a smaller pipe would increase pressure and slow the exhaust speed, not increase it.

For example, with a smaller exhaust pipe, the exhaust gasses would take longer to travel from the engine to the end of the pipe.
 
Originally Posted by ka9mnx
Originally Posted by WyrTwister
Do not know about now , exhaust systems seem to last longer . But back in the day , they tended to rust out twice as fast , especially when short tripped . Did not get hot enough to evaporate the water / moisture form the inside of the system .

Exhaust systems today are stainless steel. Back in the day they were cold rolled mild steel.

Absolutely. Today's exhaust systems last longer. When my mom had her 1964 Ford Galaxie 500 convertible which got short tripped daily, she had new mufflers every year.

Semi off topic, but my old F-150 has a straight six and true dual exhaust.
wink.gif
 
Originally Posted by userfriendly
I always thought a smaller pipe would increase pressure and slow the exhaust speed, not increase it.

For example, with a smaller exhaust pipe, the exhaust gasses would take longer to travel from the engine to the end of the pipe.


There is the optimum size for a given rpm. Everything else is a compromise. Too small and you'll choke the engine. To big and it's gutless under a certain rpm.

A smaller pipe will encourage higher exhaust gas velocities and exhaust gas scavenging. But, as rpm increases that smaller pipe can start to become a restriction.
 
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Velocity is dependent on the ability of the volume of air, or in this case exhaust having the ability to fill the pipe that it is using. think about it in terms of if you were to hook a fire hose up to your homes water system. It would just trickle out of the spigot. But when you use a regular garden hose it comes out very fast. Not a apples to apples comparison precisely, but it goes to show that if the exhaust volume is not enough to fill the pipe effectively, velocity will suffer.
 
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The exhaust "volume" would be the same as mass of the air and fuel going into the engine. It's expanded in volume due to being heated during combustion, which reduces its density

How fast is the exhaust travelling? For inertia to have a scavenging effect, such a small mass must have an extremely high velocity. I've read in magazines that the velocity is near the speed of sound.

That doesn't seem very fast for such a small mass to have enough energy to do much work.
 
Easier packaging, better looking, cost more.

Imagine your single exhaust being 1.4 times wider in diameter, it may not look good.

This is assuming the same volume flow, apple to apple comparison, between the single and dual exhausts.
 
Originally Posted by Garak

Semi off topic, but my old F-150 has a straight six and true dual exhaust.
wink.gif


EFI exhaust manifolds?

My 300 now has a Walker Y-pipe and converter assembly, after the stock cat rotted off. Fired it up after shopping, and wondered why it was so loud.
 
Originally Posted by Skippy722
....

Through all that you get engines like FCA's 305hp Pentastar V6 that makes 90+% of peak torque from a mere 1800rpm and carry it all the way to 6,350rpm while running on regular 87 octane!
I Had a rental in FLA a couple years ago for a week. Must of had a ringer motor - that V6 in a Dodge Charger was incredible punchy, quick and fast. I wanted to buy that car and bring her home to New Hampshire! And I had a '67 SS396 and '69 428CJ Fairlane 500 in my youth. Back when you could buy a 10 year old muscle car in good shape for well under a thousand bucks.
 
Originally Posted by OVERKILL
They'd be the EFI ones, they kinda look a bit like cast headers? My '88 had them on its 300.

Yes, that would be a good description. So, that would be them.
 
Originally Posted by Garak
Originally Posted by OVERKILL
They'd be the EFI ones, they kinda look a bit like cast headers? My '88 had them on its 300.

Yes, that would be a good description. So, that would be them.

EFI manifolds have 2 exhaust pipe outlets.
 
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